I have had the same issue on both my 2016 XLT and 2017 Premiere Tahoe's that the Chevy service departments cannot troubleshoot. Randomly, while driving, I hear what appears to be a rapid de-compression or release of air on the right rear underside of the vehicle as if a pressure relief valve is exceeded allowing compressed air to escape. I do not experience any driving performance issues but the sound is very obvious, concerning and cannot be normal. Is anyone else having similar experiences?